读书笔记-2019年03月04日

 @[toc]

今日见闻

• doocs/advanced-java: ? 互联网 Java 工程师进阶知识完全扫盲
• li-xiaojun/XPopup: ?功能强大，UI简洁，交互优雅的通用弹窗！可以替代Dialog，PopupWindow，PopupMenu，BottomSheet，DrawerLayout，Spinner等组件，自带十几种效果良好的动画， 支持完全的UI和动画自定义！(Powerful and Beautiful Popup，can absolutely replace Dialog，PopupWindow，PopupMenu，BottomSheet，DrawerLayout，Spinner. With built-in animators , very easy to custom Popup View.)
• macrozheng/mall: mall项目是一套电商系统，包括前台商城系统及后台管理系统，基于SpringBoot+MyBatis实现。 前台商城系统包含首页门户、商品推荐、商品搜索、商品展示、购物车、订单流程、会员中心、客户服务、帮助中心等模块。 后台管理系统包含商品管理、订单管理、会员管理、促销管理、运营管理、内容管理、统计报表、财务管理、权限管理、设置等模块。
• didi/DoraemonKit: 简称 “DoKit” 。一款功能齐全的客户端（ iOS 、Android ）研发助手，你值得拥有。
• spring-projects/spring-boot: Spring Boot
• javagrowing/JGrowing: Java is Growing up but not only Java。Java成长路线，但学到不仅仅是Java。
• alibaba/fescar: Fescar is an easy-to-use, high-performance, java based, open source distributed transaction solution.
• eugenp/tutorials: The “REST With Spring” Course:

今日重要的三件事

记录

【树莓派】通过SSH使用树莓派 - 走在冷风中的博客 - CSDN博客

通过FTP软件树莓派（Raspberry Pi 3）可以和电脑上传或者下载文件 - ZoharAndroid的博客 - CSDN博客

Error occurred during initialization of VM java/lang/NoClassDefFoundError: java/lang/Object - 热爱bug的亮蛋儿的博客 - CSDN博客

我的机器mac Os 的gcc

gcc -v
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.11.45.5)
Target: x86_64-apple-darwin18.2.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

CodeList 3-2

/* print1.c -- 说明printf()的一些属性 */
#include 
int main(void)
{
    int ten = 10;
    int two = 2;
    printf("Doing it right: ");
    printf("%d minus %d is %d\n", ten, 2, ten - two);
    printf("Doing it wrong: ");
    printf("%d minus %d is %d\n",ten);//缺少两个参数
    return 0;
}

也能编译链接成功，有一个警告⚠️。

Panda-MBP:CodeList3-2 panda8z$ gcc -o print1.out print1.c 
print1.c:10:23: warning: more '%' conversions than data arguments [-Wformat]
    printf("%d minus %d is %d\n",ten);//缺少两个参数
                     ~^
1 warning generated.

Panda-MBP:CodeList3-2 panda8z$ ./print1.out 
Doing it right: 10 minus 2 is 8
Doing it wrong: 10 minus 0 is 1071055023
Panda-MBP:CodeList3-2 panda8z$ 

CodeList 3-3

/* bases.c -- 以十进制,八进制,十六进制形式输出100 */
#include 
int main(void)
{
    int x = 100;
    printf("dec = %d; octal = %o; hex = %x\n", x, x, x);
    printf("dec = %d; octal = %o; hex = %#x\n", x, x, x);
    return 0;
}

Panda-MBP:CodeList3-3 panda8z$ gcc -o bases.out bases.c
Panda-MBP:CodeList3-3 panda8z$ ./bases.out
dec = 100; octal = 144; hex = 64
dec = 100; octal = 144; hex = 0x64
Panda-MBP:CodeList3-3 panda8z$ 

CodeList 3-4

/* print2.c -- printf()的更多属性 */
#include 
int main(void)
{
    unsigned int un = 3000000000; //int为32位
    short end = 200;              //short为16位系统
    long big = 6537;
    long long verybig = 12345678908642; //14位数

    printf("un = %u and not %d\n", un, un);
    printf("end = %hd and %d\n", end, end);
    printf("big = %1d and not %hd\n", big, big);
    printf("verybig = %1ld and not %1d\n", verybig, verybig);
    return 0;
}

Panda-MBP:CodeList3-4 panda8z$ gcc -o print2.out print2.c 
print2.c:12:39: warning: format specifies type 'int' but the argument has type 'long' [-Wformat]
    printf("big = %1d and not %hd\n", big, big);
                  ~~~                 ^~~
                  %1ld
print2.c:12:44: warning: format specifies type 'short' but the argument has type 'long' [-Wformat]
    printf("big = %1d and not %hd\n", big, big);
                              ~~~          ^~~
                              %ld
print2.c:13:44: warning: format specifies type 'long' but the argument has type 'long long' [-Wformat]
    printf("verybig = %1ld and not %1d\n", verybig, verybig);
                      ~~~~                 ^~~~~~~
                      %1lld
print2.c:13:53: warning: format specifies type 'int' but the argument has type 'long long' [-Wformat]
    printf("verybig = %1ld and not %1d\n", verybig, verybig);
                                   ~~~              ^~~~~~~
                                   %1lld
4 warnings generated.
Panda-MBP:CodeList3-4 panda8z$ ./print2.out 
un = 3000000000 and not -1294967296
end = 200 and 200
big = 6537 and not 6537
verybig = 12345678908642 and not 1942899938
Panda-MBP:CodeList3-4 panda8z$ 

CodeList 3-5

/* charcode.c -- 显示一个字符的编辑值 */
#include 
int main(void)
{
    char ch;
    printf("Please enter a charactr.\n");
    scanf("%c", &ch);
    printf("The code for %c is %d.\n", ch, ch);
    return 0;
}

Panda-MBP:CodeList3-5 panda8z$ gcc -o charcode.out charcode.c 
Panda-MBP:CodeList3-5 panda8z$ ./charcode.out 
Please enter a charactr.
rri
The code for r is 114.
Panda-MBP:CodeList3-5 panda8z$ 

CodeList 3-6

/* altnames.c -- 可移植的整数类型名 */
#include 
#include  //支持可移植类型
int main(void)
{
    int16_t me16; // me16是一个16位有符号变量
    me16 = 4593;
    printf("First, assume int16_t is short: ");
    printf("me16 = %hd\n",me16);
    printf("Next, let`s not make any assumptions. \n");
    printf("instead, use a \"macro\" from inttypes.h: ");
    printf("me16 = %" PRId16 "\n",me16);
    return 0;

}

Panda-MBP:CodeList3-6 panda8z$ gcc -o altnames.out altnames.c 
Panda-MBP:CodeList3-6 panda8z$ ./altnames.out 
First, assume int16_t is short: me16 = 4593
Next, let`s not make any assumptions. 
instead, use a "macro" from inttypes.h: me16 = 4593
Panda-MBP:CodeList3-6 panda8z$ 

CodeList 3-7

书上写的源程序真正在我的mac os上编译的时候有问题，在log里可以看出

/* showf_pt.c -- 以两种方式显示浮点值 */
#include 
int main(void)
{
    float aboat = 32000.0;
    double abet = 2.14e9;
    long double dip = 5.32e-5;
    printf("%f can be written %e\n", aboat, aboat);
    printf("%f can be written %e\n", abet, abet);
    printf("%f can be written %e\n", dip, dip);
    return 0;
    
}

编译有问题的源程序。提示使用%Lf和%Le

Panda-MBP:CodeList3-7 panda8z$ gcc -o showf_pt.out showf_pt.c 
showf_pt.c:10:38: warning: format specifies type 'double' but the argument has type 'long double' [-Wformat]
    printf("%f can be written %e\n", dip, dip);
            ~~                       ^~~
            %Lf
showf_pt.c:10:43: warning: format specifies type 'double' but the argument has type 'long double' [-Wformat]
    printf("%f can be written %e\n", dip, dip);
                              ~~          ^~~
                              %Le
2 warnings generated.
Panda-MBP:CodeList3-7 panda8z$ ./showf_pt.out 
32000.000000 can be written 3.200000e+04
2140000000.000000 can be written 2.140000e+09
2140000000.000000 can be written 2.140000e+09
Panda-MBP:CodeList3-7 panda8z$ 

改成下面这样才能正常

/* showf_pt.c -- 以两种方式显示浮点值 */
#include 
int main(void)
{
    float aboat = 32000.0;
    double abet = 2.14e9;
    long double dip = 5.32e-5;
    printf("%f can be written %e\n", aboat, aboat);
    printf("%f can be written %e\n", abet, abet);
    printf("%Lf can be written %Le\n", dip, dip);
    return 0;
    
}

Panda-MBP:CodeList3-7 panda8z$ gcc -o showf_pt.out showf_pt.c 
Panda-MBP:CodeList3-7 panda8z$ ./showf_pt.out 
32000.000000 can be written 3.200000e+04
2140000000.000000 can be written 2.140000e+09
0.000053 can be written 5.320000e-05
Panda-MBP:CodeList3-7 panda8z$ 

CodeList 3-8 at P52

/* typesize.c -- 输出类型的大小 */
#include 
int main(void)
{
    /* c99为类型大小提供一个%zd说明符 */
    printf("Type int has a size of %u bytes.\n",sizeof(int));
    printf("Type char has a size of %u bytes.\n", sizeof(char));
    printf("Type long has a size of %u bytes.\n", sizeof(long));
    printf("Type double has a size of %u bytes.\n", sizeof(double));
    return 0;

}

按照书上代码写有问题,但是这里还是没影响到执行结果。

Panda-MBP:CodeList3-8 panda8z$ gcc -o typesize.out typesize.c 
typesize.c:6:49: warning: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Wformat]
    printf("Type int has a size of %u bytes.\n",sizeof(int));
                                   ~~           ^~~~~~~~~~~
                                   %lu
typesize.c:7:51: warning: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Wformat]
    printf("Type char has a size of %u bytes.\n", sizeof(char));
                                    ~~            ^~~~~~~~~~~~
                                    %lu
typesize.c:8:51: warning: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Wformat]
    printf("Type long has a size of %u bytes.\n", sizeof(long));
                                    ~~            ^~~~~~~~~~~~
                                    %lu
typesize.c:9:53: warning: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Wformat]
    printf("Type double has a size of %u bytes.\n", sizeof(double));
                                      ~~            ^~~~~~~~~~~~~~
                                      %lu
4 warnings generated.
Panda-MBP:CodeList3-8 panda8z$ ./typesize.out 
Type int has a size of 4 bytes.
Type char has a size of 1 bytes.
Type long has a size of 8 bytes.
Type double has a size of 8 bytes.

能看得出 在现在的这台MacOS上 long和double都是8个字节。也就是都是64个二进制位。

CodeList 3-9 at P54

/* badcount.c -- 不正确的参数个数 */
#include 
int main(void)
{
    int f = 4;
    int g = 5;
    float h = 5.0f;

    printf("%d\n", f, g); //参数太多
    printf("%d %d\n", f); //参数太少
    printf("%d %f\n", h, f); //参数类型不匹配
    return 0;
}

Panda-MBP:CodeList3-9 panda8z$ gcc -o badcount.out badcount.c 
badcount.c:9:23: warning: data argument not used by format string [-Wformat-extra-args]
    printf("%d\n", f, g); //参数太多
           ~~~~~~     ^
badcount.c:10:17: warning: more '%' conversions than data arguments [-Wformat]
    printf("%d %d\n", f); //参数太少
               ~^
badcount.c:11:23: warning: format specifies type 'int' but the argument has type 'float' [-Wformat]
    printf("%d %f\n", h, f); //参数类型不匹配
            ~~        ^
            %f
badcount.c:11:26: warning: format specifies type 'double' but the argument has type 'int' [-Wformat]
    printf("%d %f\n", h, f); //参数类型不匹配
               ~~        ^
               %d
4 warnings generated.
Panda-MBP:CodeList3-9 panda8z$ ./badcount.out 
4
4 0
4 5.000000

CodeList 3-10 at P55

/* escape.c -- 使用转义字符 */
#include 
int main(void)
{
    float salary;
    printf("\aEnter your desired monthly salary: ");
    printf(" $_____\b\b\b\b\b\b\b");
    scanf("%f", salary);
    printf("\n\t$.2f a month is $.2f a year.", salary, salary * 12.0);
    printf("\rGee!\n");
    return 0;
}

Panda-MBP:CodeList3-10 panda8z$ gcc -o escape.out escape.c 
escape.c:8:17: warning: format specifies type 'float *' but the argument has type 'double' [-Wformat]
    scanf("%f", salary);
           ~~   ^~~~~~
escape.c:9:48: warning: data argument not used by format string [-Wformat-extra-args]
    printf("\n\t$.2f a month is $.2f a year.", salary, salary * 12.0);
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  ^
2 warnings generated.
Panda-MBP:CodeList3-10 panda8z$ ./escape.out 
Enter your desired monthly salary:1200___
Segmentation fault: 11
Panda-MBP:CodeList3-10 panda8z$ 

正确的程序如下：

/* escape.c -- 使用转义字符 */
#include 
int main(void)
{
    float salary;
    printf("\aEnter your desired monthly salary: ");
    printf(" $_______\b\b\b\b\b\b\b");
    scanf("%f", &salary);
    printf("\n\t$%.2f a month is $%.2f a year.", salary, salary * 12.0);
    printf("\rGee!\n");
    return 0;
}

正确的输出如下：

Panda-MBP:CodeList3-10 panda8z$ gcc -o escape.out escape.c 
Panda-MBP:CodeList3-10 panda8z$ ./escape.out 
Enter your desired monthly salary:  $1234567

Gee!    $1234567.00 a month is $14814804.00 a year.
Panda-MBP:CodeList3-10 panda8z$